At present, telephony service applications are partitioned between the Public Switched Telephone Network (PSTN) and Internet Protocol (IP) networks. That is, the PSTN, either at a service switching point (SSP) or a service control point (SCP), does not look to an IP-based application server to augment its call processing procedures. Likewise, voice over IP (VoIP) approaches assume that control, or responsibility, for a call has been completely transferred to an IP-based application server. The emphasis in interworking has been in the signaling and control plane, not the application plane. For example, PSTN subscribers are currently offered telephony services, such as Call Waiting and Call Forwarding, through features that are provided by Central Office Switching Systems vendors and their local exchange carriers. In addition, the Advanced Intelligent network (AIN) offers PSTN users an advanced set of enhanced telephony services through the use of AIN Triggers during the originating or terminating points in a call. The SCP conventionally runs service logic based on the AIN triggers and instructs the SSP on call completion.
Furthermore, VoIP may include calls originating or terminating on-IP network and calls originating or terminating off-IP network. In cases where the PSTN is involved, this usually means that a call starts or ends in the PSTN, but is sent to the IP network via a PSTN/IP gateway. Once the call transfers through this gateway, application layer responsibility for the call moves to the IP-based application server. This server works independently of the SCP. This approach, thus, is inherently inefficient for incumbent PSTN carriers and requires the deployment of an IP network capable of meeting the business/service requirements associated with voice traffic and services. Furthermore, considering the disjoint nature of PSTN/VoIP application layer evolution, no attention has been paid toward finding methods and systems to allow the application layer components in each environment (network) to leverage the developments of the other.
Therefore, there exists a need for systems and methods that can implement an integrated telephony service infrastructure that has the capability to leverage and build on the embedded AIN infrastructure and the PSTN customer base with IP application.